"Shooting Star Bow – Ceal" decreases the current ATK. So if "Injection Fairy Lily" is equipped with "Shooting Star Bow – Ceal" and activates her effect, her ATK is 2400 ((400 – 1000) + 3000 = 2400).
If a monster equipped with "Shooting Star Bow – Ceal" declares a direct attack, and "Shooting Star Bow – Ceal" is removed from the monster during the Battle Step with "Mystical Space Typhoon" or "Tailor of the Fickle", the monster is no longer capable of attacking directly and a replay occurs.
"Tyrant Dragon" must attack a monster in order to gain its second attack, so if it is equipped with "Shooting Star Bow – Ceal" and attacks directly, it cannot get a second attack. But "Tyrant Dragon" equipped with "Shooting Star Bow – Ceal" can attack a monster, and then attack directly.